This invention relates to a lubricating oil system for a vertically disposed gear unit and in particular, to a purge system for returning lubricating oil from a lower collecting sump to an upper supply sump of the gear unit.
Vertical gear units wherein the motor is affixed to the top of a shaft and a driven member is affixed to the bottom of the shaft are used in many applications. It is quite difficult to seal the output shaft at its lower end because of the shaft's high speed. Accordingly, the gear unit generally includes a lower sump for collecting lubricating oil that passes through the lower bearing of the gear unit. A mechanical suction pump is typically employed as a scavenging pump to return the oil collected in the lower sump to the main sump, generally positioned in the gear unit thereabove. Such mechanical suction pumps are relatively expensive and require, at a minimum, routine maintenance. Thus, where the gear units are installed in relatively remote locations, and in harsh environments, service of the mechanical pumps is a rather difficult endeavor.
Further, the conventional mechanical pumps require a relatively large amount of installation space. In applications where such space is at a premium, the use of conventional mechanical pumps creates a considerable problem. Yet, another problem associated with conventional scavenging pumps involves the intermittent operation of the scavenging operation itself. Since the flow of oil into the lower collecting sump is not continuous but is somewhat intermittent, continuous operation of the scavenging pump may result in undesirable cavitation thereof.
Accordingly, it is an object of this invention to eliminate the problems discussed above associated with the conventional mechanical scavenging pumps employed in lubrication systems for a vertical gear unit.